Project Summary/Abstract Eating disorders are resistant to treatment and associated with significant morbidity and mortality. Thus, efficacious and efficient eating disorder prevention programs are greatly needed. There has been a longstanding belief among the general public, and clinicians, that eating disorders are nearly an exclusively female problem. However, extant literature has found that males also experience eating disorders, constituting up to 40% of individuals with diagnostic/sub-threshold eating pathology. Among males, sexual minorities (i.e., gay, bisexual, and non-heterosexual identified individuals) are a salient subgroup that is at substantial risk for developing eating disorders. Indeed, sexual minority males are not only at elevated risk compared to heterosexual males, but are also at elevated risk compared to heterosexual females. The lifetime prevalence for any eating disorder diagnosis among sexual minority males is 8.8%, and subclinical diagnosis is 15.6%. This is in contrast to heterosexual females, in which the prevalence for clinical and subclinical diagnoses are at 4.8% and 8.0%, respectively. These findings indicate that sexual minority males may well be one of the most vulnerable groups in regard to eating pathology risk. To date, there is a paucity of research on eating disorder prevention programs among sexual minority males. We are only aware of one previous prevention program targeting sexual minority males. This program, the PRIDE Body Project, developed and tested by our research team, is a two-session, peer co-led, group, cognitive dissonance-based eating disorder prevention program, based on existing eating disorder prevention programs developed with females. In our preliminary randomized controlled trial (RCT), we found significant and large effects on eating pathology and relevant eating disorder risk factors, compared to a waitlist control condition, at post-treatment and 4-weeks post-treatment. Additionally, preliminary mediation analyses revealed that internalization of the appearance ideal and body dissatisfaction accounted for significant variance in the relationship between treatment condition and eating pathology. These results represent an important first step in demonstrating the acceptability, feasibility, and preliminary efficacy of a brief, peer-led eating disorder prevention program for sexual minority males. Despite these initial findings, future research is needed to further test this promising intervention. Specifically, it is not known if the PRIDE Body Project will exert a clinically and statistically significant effect in comparison to a time and attention matched control condition. Additionally, it is unknown if the intervention effects will persist beyond 4-weeks post intervention. With these limitations in mind, we propose to conduct a randomized controlled trial assessing the PRIDE Body Project to a time and attention-matched active control condition, and follow participants for 24 months. Additionally, we plan to assess potential mediators (body dissatisfaction and internalization of the appearance ideal) of the treatment effect on eating disorder symptoms.